This invention relates to a heater unit which is adapted to an air-conditioning device in automotive vehicles.
There have so far been known the heater unit of a construction such that, with a view to attaining the head-cooling-feet-warming mode, cool air current which has passed through an evaporator is introduced into an inlet or suction opening of the heater unit, and the thus introduced cool air current is divisively distributed by a distributing damper provided within the heater unit so that cool air, as it is may be discharged upwardly into the vehicle compartment or cabin through an upwardly directing outlet opening, while warm air obtained by causing a portion of the introduced cool air current to pass through a heat exchanger within the heater unit may be discharged downwardly into the vehicle cabin through a downwardly directing outlet opening.
In the heater unit of the above-described type, since major portion of warm air current which has passed through the heat exchanger is discharged almost directly downward of the vehicle cabin, for example, to the defroster, or to the feet of the riders, there inevitably occurs such phenomenon that the temperature only at the lower part of the vehicle cabin rapidly increases to cause excessive temperature difference between the upper and lower parts in the vehicle cabin, which has been the problem in controlling the temperature for its appropriate and uniform distribution. Further, there is such inconvenience that, when a trouble occurs in the heater unit at the time of the cooling operation, the cool air current becomes unavoidably heated.